Such corrugated tubes are generally fabricated continuously by extrusion (or by co-extrusion for multilayer tubes).
In order to couple a corrugated tube to a coupling, it is known, during extrusion, to provide a smooth zone at the end of the corrugated tube for receiving a coupling that is provided on the outside with annular barbs in a Christmas-tree configuration. Making such a smooth portion on the tube requires special tooling and leads to a reduction in the speed of extrusion, thereby increasing the cost of manufacturing the tube.
It is also known to make a smooth portion at the end of the tube by overmolding a lining of plastics material. That likewise increases the time needed for manufacturing the tube and the cost thereof.
It might be thought that a coupling endpiece having conventional Christmas-tree-shaped barbs could be used with a tube having corrugated ends merely by forcing the endpiece directly into one of the corrugated ends of the tube. However the reliability of such a coupling would be uncertain because of the tendency of the tube to inflate under pressure, which would run the risk of the tube separating from the endpiece.
One way of remedying that drawback would be to reinforce the end of the corrugated tube on the outside in order to restrict deformation thereof. Such reinforcement could be achieved while making the corrugated tube (e.g. by overmolding a rigid ring), but that would return to the above-mentioned drawback concerning lengthening the time needed to manufacture the tube and increasing its cost, or the time needed during assembly (e.g. by putting a clamping collar or the like into place), but then that would increase assembly costs.